1. Technical Field
The present invention pertains to surgical warming systems for heating various items. In particular, the present invention pertains to a warming system and method for heating intravenous (IV) solution contained within bags and/or bottles, surgical instruments, blood and drugs placed within appropriate containers, or other objects for use in surgical procedures.
2. Discussion of Related Art
Generally, various items are required to be heated prior to utilization in a medical procedure to prevent thermal shock and injury to a patient. These items typically include intravenous solution, surgical instruments, bottles and blankets. In order to provide the necessary heated items for use in medical procedures, medical personnel may utilize several types of warming systems to heat items toward their operational temperatures. For example, ovens may be disposed within operating rooms to heat items to desired temperatures. Further, U.S. Pat. No. 4,495,402 (Burdick et al) discloses a warmer for heating wet dressings and other articles disposed within a heating and storage compartment. The articles are arranged within the compartment in stacked relation and disposed on a plate that is supplied with thermal energy from a heater. The plate includes a center aperture whereby a first thermal sensor is disposed in the aperture in contact with a bottommost article. Control circuitry is disposed beneath the plate to control the heater to maintain temperature of the bottommost article at a desired level based on the temperatures sensed by the first thermal sensor and a second thermal sensor responsive to heater temperature.
U.S. Pat. No. 5,408,576 (Bishop) discloses an intravenous fluid warmer having a cabinet structure to accommodate a plurality of intravenous fluid bags. A temperature sensor and pad of heating filaments are disposed within the cabinet structure, whereby the temperature sensor measures the pad temperature and enables automatic temperature regulation of the pad to heat the intravenous fluid bags. The heating filaments are covered by a rubber layer to prevent melting of the bags during heating. A temperature indicator connected to the temperature sensor and disposed on the cabinet structure permits a user to ascertain when a desired temperature is attained, whereby an intravenous fluid bag is removed from the intravenous fluid warmer via an opening defined in a side of the cabinet structure.
The warming systems described above suffer from several disadvantages. In particular, ovens typically do not have a high degree of accuracy or control, thereby enabling use of items having temperatures incompatible with a medical procedure and possibly causing injury to a patient. Further, the Burdick et al and Bishop warmers employ heaters that generally contact a portion of the article being heated, thereby heating the articles in an uneven manner and enabling formation of hot spots. Moreover, the Burdick et al and Bishop warmers generally permit direct contact between an article and a heater, thereby enabling the article to become damaged from excess heat.
In order to overcome the aforementioned problems, some warming systems utilize heated air to heat articles placed within these systems. For example, U.S. Pat. No. 5,282,264 (Reeves et al) discloses an apparatus for thawing and warming solutions or fluids for intravenous administration. The solutions are typically contained within bags and placed within a tray disposed toward the top of an apparatus cabinet. A heating element is disposed within the apparatus cabinet whereby an impeller forces air past the heating element and into an air plenum. The air plenum extends from within the apparatus cabinet and curves over the top of the tray to direct and evenly distribute the heated air over various articles placed in the tray. A temperature sensor measures air temperature to enable a controller to maintain the heated air within a desired temperature range.
U.S. Pat. No. 5,297,234 (Harms et al) discloses an apparatus for rapid thermal processing of transfusion fluid, such as blood or blood components. The apparatus thaws a bag containing frozen blood or blood components by directing a flow of air across a heating coil. Temperature sensors measure the temperatures of the air and blood, whereby a control system monitors the sensed air temperature to maintain air temperature at a particular level, and terminates thawing in response to a bag temperature of 30° C. The apparatus further enables rapid freezing of blood by directing air across a cooling coil and upon a bag containing blood to freeze that blood. The control system monitors sensed blood temperature via the temperature sensor, and terminates freezing in response to a bag or blood temperature of −30° C. The control system further facilitates display of the sensed bag temperatures on an operator display.
The warming systems described above utilizing heated air to warm items suffer from several disadvantages. In particular, the warming systems heat items simultaneously to only a single desired temperature, thereby being incompatible for applications requiring various items to be heated to different temperature ranges. Further, the warming systems control item temperature based on temperature of flowing air measured within a compartment separate from the items, thereby providing less accurate temperature control of the item storage compartment and for maintaining items at a desired temperature. Moreover, the warming systems have fixed storage capacities and are limited to a certain quantity or size of items, thereby being incompatible with items having dimensions beyond those of the respective system storage capacities, and/or requiring use of additional systems or heating cycles to accommodate additional items. Conversely, the warming systems may utilize excess resources when used for quantities of items substantially less than their storage capacities. In addition, the above-described warming systems do not provide an indication of the amount of time items reside within the systems. Thus, medical personnel may unknowingly administer to patients solutions and/or medication that are unusable and/or have reduced potency due to prolonged exposure to heat, thereby risking serious injury to the patients.